Rradiation Damage Analysis Of GaInP/GaAs/Ge Solar Cells

GaAs solar cells are the main source of energy for spacecraft in space.However,solar cells in space are exposed to space particles,causing damage in the solar cell.In this paper,the radiation damage characteristics of GaInP/GaAs/Ge triple-junction solar cells and their GaAs sub-cells are systematically studied by means of current-voltage,spectral response?EQE?and fluorescence spectroscopy?PL?.The main findings are:?1?The GaInP/GaAs/Ge triple junction solar cell for satellite was used as the research object.The radiation damage of the solar cell was studied by proton and helium ion irradiation experiments.The results show that the degradation of the electrical properties of the triple-junction GaInP/GaAs/Ge after high-energy proton and heavy ion irradiation also conforms to the engineering application formula,I_SC presents a more serious degradation behavior,mainly due to the series structure of the solar cell.The quantum efficiency test of the heavy ion irradiated solar cell shows that the top cell of the solar cell is more seriously damaged by heavy ions than the middle cell,mainly because the base of the intermediate cell is thicker,resulting in the photogenerated current generated by the cell in the base region.The photo-generated carrier is captured by the recombination center,resulting in a decrease in the photoelectric conversion efficiency of the solar cell.The photoluminescence test also showed that the photoluminescence spectrum of the solar cell has a characteristic peak at 650 nm.The half-peak width of the photoluminescence spectrum of the GaInP material after irradiation is obviously larger and the peak position is more obvious than that before the irradiation.The left shift is mainly due to the destruction of the lattice integrity after irradiation,and the lattice atoms will appear partially irregularly arranged.?2?GaAs sub cells in triple-junction cells are most susceptible to radiation damage.Therefore,150keV proton irradiation damage is studied separately for GaAs sub-cells.The results show that the degradation of GaAs electrical properties is logarithmic with the irradiation fluence.The results of quantum efficiency indicate that the damage of the base of the GaAs solar cell after irradiation is severe,which is attributed to the decrease of minority carrier lifetime.Based on the results of deep-level tests,it is found that the GaAs solar cells with low radiation fluence are similar to those before irradiation,and there are no deep-level defects,but when the irradiation fluence reaches to 5×10¹¹ cm^-2,the defect level of 0.491 eV,the capture interface is 6.95×10^-14 cm²,and the concentration is 5.91×10¹⁵ cm^-33 can be tested in GaAs.At the same time,based on the photoluminescence test results of solar cells,it is known that the composite of minority carriers of GaAs is mainly composed of radiative minority carriers before irradiation,and after irradiation to a certain extent,the composite mode in the solar cell is mainly non-radiative composite.The main reason for the decrease in electrical performance after irradiation is due to the decrease in the lifetime of the non-radiative minority carriers in the solar cell,and it is known that the solar cell is irradiated under the irradiation of 3×10¹⁰,1×10¹¹,5×10¹¹ cm^-2,the non-radiative composite minority carrier lifetimes in the medium are 2.22 ns,0.67 ns,0.13 ns.?3?Based on the results of GaAs sub cells and the finite element simulation method,the effects of different minority carrier lifetimes on solar cell performance were investigated.The results show that the solar cell model of the solar cell in the original state and the irradiation damage state is established by adjusting the minority carrier lifetime.The decrease in lifetime of the minority carrier causes changes in the energy band structure and the internal current of the solar cell,which in turn causes a change in macroscopic electrical properties.Based on this,the degradation model of GaAs in different orbits is established,which relates the environmental damage effect of space irradiation,the degradation of minority carrier lifetime and electrical performance,and predicts the degradation of electrical performance of solar cells during in-orbit service.